Pretty much anything not covered by the topics above. Short lived production bikes or vehicles, Electrical, Tires, Paint, Brakes, etc. Use this for tech questions, and "Shoot the Bull" for general conversation, no tech.
Good Question PA Single row primary with the drive sprocket on the right, its definetly older than a '29 and its definetly not a big twin. The box for the big twin sliding gear 3 speeds goes all the way back to the beginning in 1915. My guess is that its also a sliding gear but probably for a single from the early 20's.